Silo closure actuation

ABSTRACT

A missile silo for enclosing the missile prior to launch. The silo includes a closure (door) which is hardened against nuclear induced overpressure, ground shock, and radiation to provide a massive structure, usually of concrete and steel construction. Silo closure actuation means is provided to open the door to permit launching of the missile. No source of power, other than missile propellant energy is required for opening the door.

Unite 101 States Patent [191 Osborn, jr.

[ SILO CLOSURE ACTUATlON [75] Inventor: Garland W. Osborn, jr., FountainValley, Calif.

[73] Assignee: The United States of America as represented by theSecretary of the Army, Washington, DC.

[22] Filed: June 20, 1973 [21] Appl. No.: 372,882

[52] US. Cl. 89/1.8, 89/1817 [51] Int. Cl F4lf 3/04 [58] Field of Search89/18, 1.815, 1.816, 1.817, 89/1818, 1.819, 30, 31, 1.812; 252/478;102/42 C [56] References Cited UNITED STATES PATENTS 587,734 8/1897Hammer 89/31 3,031,932 5/1962 Fite, .lr 89/1812 3,148,472 9/1964 Heggeet al 102/93 X 3,225,655 12/1965 Inglis 89/1816 3,261,800 7/1966 Collins252/478 X 3,355,985 12/1967 Gauss et a1. 89/1816 3,599,568 8/1971Shellnutt 102/42 C 3,610,095 10/1971 Black et a1 89/18 3,644,236 2/1972Macoustra 252/478 X Primary ExaminerSamuel W. Engle Attorney, Agent, orFirm-Lawrence A. Neureithcr; Leonard Flank; Harold W. Hilton 2 Claims, 2Drawing Figures SILO CLOSURE ACTUATION BACKGROUND OF THE INVENTIONHardened defense interceptors (and ICBMS) are protected by massive silodoors which shield against nuclear radiation and protect againstoverpressure. The time required to open the silo for launch is of greatimportance to the launch envelope and vulnerability of the missile whenthe site is under heavy attack. Present closures require large andcostly mechanisms for opening and as presently designed, take manyseconds, and often minutes to remove for launch.

SUMMARY OF THE INVENTION The above noted difficulties are overcome byapparatus of the present invention which utilizes missile propellantenergy for silo closure actuation, thus permitting great reductions inopening time and silo cost. A foam material is disposed for encasing themissile dur' ing storage thereof in the silo. The foam material encasesthe missile and extends upwardly therefrom in proximity of the door. Thefoam-encased missile pushes against the segmented silo door as it risesin the first travel of launch. As the door clears the silo portal (andcovering debris), its segments are deflected aside from the foamcovering. The foam remains around the missile until the door has beencleared.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view,partially in section, of a foam encased missile in a silo.

FIG. 2 is an elevational view, partially in section, similar to FIG. 1,showing the initial movement of the missile opening the silo door.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the figures, a siloincludes an annular wall 12 forming a chamber 14 having a missile 16therein. A closure member 18 having a pair of segments 20 and 22 isdisposed atop the silo for sealing the missile therein. A foam material24 encases missile l6 and extends upwardly in proximity of closuremember 18. A portion of the foam is disposed between the nose of themissile and the closure member. A gap 28 is left between the upper end26 of foam 24 and the underside of closure member 18, to provide arattle-space for accommodating nuclear-induced ground shock.

The foam material 24 may be comprised of a pair of semi-cylindricalsections placed around the missile and held in place by annular wall 12of the silo.

As seen in the Figures, the underside of the closure segments 20 and 22are tapered upwardly to the line of contact between the segments. Thesections of foam material 20 are provided with upper surfaces which aretapered in parallel relation to the tapered surfaces of the closuresegments. The tip of the missile is aligned with the line of contact ofthe closure segments.

The silo closure (door) is hardened against nuclear inducedoverpressure, ground shock, and radiation, resulting in a massivestructure, usually of concrete and steel construction. The closure isrestrained in place to the surrounding silo portal by electro-explosiveattachments such as explosive bolts (not shown). When the signal tolaunch the missile is received, these attachments are released freeingthe closure segments from the silo portal and from each other.

Concurrently, the launch tube plenum chamber 25 (beneath the missile) ispressurized by igniting a gas generator or by igniting the mainpropellant motor(s). In the latter case, the burning area of thepropellant grain is reduced by thrust inhibiting material. This reducesthe total mass flow of the burning missile propellants sufficiently sothat the missile acceleration does not exceed the allowable compressivestress of the foam material between the missile and the closure. When agas generator is used, its burning rate is designed to provide anincreasing mass flow to coincide with the expanding plenum chambervolume created as the missile rises.

At launch, the missile and the column of foam rises in response to theexpanding plenum chamber volume to contact the underside of the closureand to subse quently raise the closure segments clear of the surroundingsilo portal (FIG. 2). Once clear of the portal, the closure segments arefree to separate and fall clear of the foam/missile.

The foam remains around the missile until the launch tube is nearlycleared, providing protection to the missile from debris which mightcover the silo door prior to launch. The foam might be compounded frompolyethylene and polyurethane which gives additional protection againstfast neutrons, resulting from nuclear detonations in the vicinity of thesilo. Secondary gamma rays are absorbed by boron additives in the foamand within the door shielding material.

The rate of missile acceleration is determined by the strength of thefoam material and the allowable unit pressures transmitted to the skinof the missile. This acceleration rate is constrained by the density ofthe foam, the mass of the closure. and the weight ofdebris which mightbe present on the top of the closure. The mass flow of the ejectinggasses must be tailored to these conditions to achieve a minimum exittime without exceeding the foam and missile allowable forces.

The closure is segmented, to reduce the time required to clear themissile flight path and to reduce the sideforce applied to the foamsurrounded interceptor. The contacting foam and the underside of theclosure are angled away from the separation joint between the seg mentsto aid segment separation.

I claim:

1. In a silo enclosing a missile, said silo having massive segmentedclosure members provided with underside surfaces tapered upwardly to thepoint ofjuncturc of said closure members, means for rapidly opening saidclosure members comprising: foam means carried around said missile andextending upwardly between the nose of the missile and said closuremembers, said foam means having upper surfaces tapered in parallelrelation to said tapered surfaces of said closure members and disposedin spaced relation with said closure members; and, means for propellingsaid missile upwardly whereby said tapered surfaces of said foammaterial engages said tapered surfaces of said closure members fordisplacement thereof.

2. Apparatus as in claim 1 wherein said foam means is provided withboron additives for absorption of secondary gamma rays.

1. In a silo enclosing a missile, said silo having massive segmentedclosure members provided with underside surfaces tapered upwardly to thepoint of juncture of said closure members, means for rapidly openingsaid closure members comprising: foam means carried around said missileand extending upwardly between the nose of the missile and said closuremembers, said foam means having upper surfaces tapered in parallelrelation to said tapered surfaces of said closure members and disposedin spaced relation with said closure members; and, means for propellingsaid missile upwardly whereby said tapered surfaces of said foammaterial engages said tapered surfaces of said closure members fordisplacement thereof.
 2. Apparatus as in claim 1 wherein said foam meansis provided with boron additives for absorption of secondary gamma rays.